Sagebrush study targets diversity to improve sage grouse habitat

The University of Idaho is conducting a study to reduce old stands of sagebrush to improve sage grouse habitat. Too dense sagebrush reduces new sagebrush, grasses and forbs and does not provide good cover for sage grouse. Pretreatment work has already been done, mechanical removal is set for end of this month. Data to be collected and evaluated next spring.

Thinning old sagebrush stands to allow younger sagebrush, native grasses and forbs to grow might provide more high-quality habitat for sage grouse, a candidate species for protection under the Endangered Species Act.

University of Idaho extension faculty members have already set a plan in motion to test that theory with a rangeland study funded by an $8,000 grant from the David Little Endowment for rangeland research.

The study is focused on evaluating the effects of mechanical treatments to reduce dense sagebrush cover and enhance sage grouse habitat, said Amanda Gearhart, University of Idaho rangeland specialist.

“A lot of people have the misconception that all sagebrush is good sage grouse habitat, and in reality that’s not always true,” she said.

As sagebrush gets denser, it tends to get decadent on the bottom. The sparse lower canopy doesn’t provide good cover for sage grouse to hide or nest, and dense stands of sagebrush reduce both diversity and quantity of native, perennial forbs and grasses that are critical for sage grouse survival, she said.

Lack of fire, due to better fire suppression as humans move further onto rural landscapes, has allowed for dense stands of older, less productive sagebrush, she said.

The study will test two mechanical treatments to remove sagebrush, with the possibility of a third chemical treatment, on approximately 640 acres of private land located in the Medicine Lodge area near Dubois in eastern Idaho. The Lawson Aerator and Dixie Harrow mechanical treatments are designed to crush the sagebrush and reduce cover.

Gearhart and her team of university students have already laid out treatment and control blocks and completed pretreatment measurements, collecting production and plant community data. Treatments are scheduled to be done at the end of September, and post-treatment data will be collected next spring.

Gearhart and John Hogge, UI extension educator for Jefferson and Clark counties, will be conducting the biological study. They will be joined by Neil Rimbey, UI extension range economist, who will study the costs associated with the treatments.

The sagebrush that is in the project site is not very productive sagebrush, Hogge said.

Removing the sagebrush will allow younger sagebrush, native grasses and forbs to grow, and the team is optimistic those habitat changes will attract more sage grouse, he said.

“There are a lot of insects that are in the area when there are lots of grasses and forbs. Sage grouse need those during late brood rearing,” he said.

Sagebrush reduction could also provide more forage for domestic livestock, he said.

Not only does the project study the biological effects of sagebrush removal but also the costs associated with the treatments.

“Some studies have started to look at these mechanical treatments but most do not include the economic aspect, which is why we wanted Neil Rimbey to join us,” Gearhart said.

As the team’s range economist, Rimbey will estimate the costs of applying each treatment, which will be of particular use to landowners and livestock producers who want to use these treatments to improve their land, she said.

The team anticipates data from the study may be used by federal and state land management agencies.

“Our primary objective is to improve sage grouse habitat, and we want to provide landowners with useful economic and ecological information about how to treat large tracts of sagebrush that are dense in cover,” Gearhart said.